AMP for email is, AIUI, a way to embed a dynamic webpage in an email, and have GMail display it. (You can see it in Google Docs comment notifications for example, which update as the document changes, and allow you to reply to the comment from inside the email.)
On the one hand there are a number of philosophical, legal and business concerns around AMP, which hands over a lot of control to Google. (There has been some prior discussion of plain AMP, which is just a way to get a website to run on Google’s servers, in How about Discourse Support Google AMP? and Discourse Comment Embed to Support Google AMP?)
On the other hand, this would help with a major usability problem for Discourse: email responses, where the software currently needs to reverse-engineer whatever rich HTML the email client produced, figure out what’s quoted and what’s actual new content, and map the HTML to markup allowed in Discourse, which is never going to be a smooth process. With AMP emails one could just use the normal Discourse authoring environment within the email.
(It would presumably also make moderation a bit more effective, as removing nasty comments would take effect even for users who have received them in email before the moderation. As long as they use GMail, anyway…)